This invention generally relates to structural reinforcement devices, and in particular to fasteners used to secure a frame member to a foundation.
Buildings and other structures are exposed to natural occurrences such as earthquakes, tornados, hurricanes and high winds which can cause damage when design loads are exceeded. Typically, damage results from either shear forces, which pull or tear apart a portion of a building, or uplifting forces, which cause separation of a structural frame of the building from its foundation. In an effort to prevent damage from shear forces, the structural frame is commonly braced or reinforced. Several approaches are explained in Hardy U.S. Pat. Nos. 6,148,583, 6,067,769 and 5,729,950.
In an effort to prevent damage from uplifting forces, the structural frame is commonly secured to the foundation using a plurality of fasteners. Building codes typically specify the required fastener length and diameter as well as their placement within the foundation. Typically, these fasteners are vertically oriented, metallic anchor bolts which extend through the structural frame and into a foundation material. An anchor bolt consists of two ends; a stud and an anchor portion. The stud, which has a threaded end, protrudes above the concrete for use in fastening a building frame to the foundation using a standard threaded nut and washer assembly. The anchor portion is commonly configured in a “J” or “L” located within the foundation to secure the bolt in the foundation. In addition, eye bolts, “U” bolts, headed bolts or headed bolts with washers are sometimes used.
The effectiveness of the anchor bolt in preventing damage is dependent on its own strength, the type of foundation material in which the anchor portion is set and the connection between the foundation material and anchor portion. The connection between the foundation material and anchor portion is established by the configuration of the anchor portion. The configurations of conventional anchors vary substantially and are dependent on whether the anchor was designed to be installed prior to or after the laying of the foundation material. Anchor portions designed to be installed after the foundation material is laid are typically bonded into holes which are pre-drilled into an existing foundation. Anchor bolts designed to be set into position prior to pouring the foundation material are usually placed into position by affixing each bolt to a metal or wooden support using bailing wire. These anchor portions are embedded in the foundation. As a result, anchor bolts with anchor portions embedded in the foundation have a substantially greater tensile capacity compared to those installed after the foundation is laid.
Unfortunately, the capability of an embedded anchor bolt to provide tensile strength to a frame member is degraded if the anchor bolt is not positioned properly, becomes misaligned during the pouring of the foundation or does not adequately penetrate the foundation. Moreover, the stud may protrude through the foundation at the wrong position making it difficult to secure the structural frame to the foundation and compromising its effectiveness. Further, the tasks of positioning and securing each anchor bolt to the support are time consuming, labor intensive and correspondingly costly.